In recent years there is a rapid advance in understanding the conditions that lead to launching of astronomical jets and their internal properties. This is expected to be further enhanced with the recent operation of the event horizon telescope (EHT), that is expected to publish its first results in 2018. In this talk, I will describe a serious of works we conducted recently aimed at testing the observational signatures that discriminates between emission from jets and accretion disks, test the jet power-black hole spin relation, jet filling factor, and explain the rapid variability seen in blazars as due of turbulence in the inner jet region.
